He switched allegiance to Turkey in June 2011, changing his name to İlham Tanui Özbilen. His surname was given him by his godfather and manager Önder Özbilen, who persuaded him in December 2010 in Kenya to immigrate to Turkey. He moved in February 2011 to Turkey, and was naturalized on 8 June 2011.[2][6] While he would normally have been ineligible to internationally represent his adoptive country until 8 June 2013,[6][7] it was announced in February 2012 that he had received permission from the International Association of Athletics Federations (IAAF) to compete for Turkey starting with the 2012 World Indoor Championships in Istanbul.[1][7][8][9]

İlham Tanui Özbilen won the silver medal for Turkey in the 1500 m event at the 2012 IAAF World Indoor Championships held in Istanbul, Turkey. Özbilen also represented Turkey at the 2012 Summer Olympics in London, where he made the final of the 1500 meters, finishing 8th, with a time of 3:36.72. At the 2013 Mediterranean Games held in Mersin, Turkey, he became gold medalist in the 1500 m event.

In 2015, Özbilen competed in the 1500 metres at the European Indoor Championships. He came second place with a time 3:37.74, behind Jakub Holuša, the national record holder in the 1500 metres for the Czech Republic.